In detail: use Test; loads the testing module, plan 6; declares that we plan to run six tests. Then five lines of the pattern is $got, $expected, $description follow. is() does string comparison, but since integers always stringify the same way, that’s fine.

Finally with dies_ok { $some_code }, $description we test that calling the function with a non-integer argument is a fatal error.

The output contains the test plan 1..6, followed by one line for each test. That starts with ok (or not ok if the test failed), the test number, space, dash, space and test description.

If you run more tests, you don’t want to look through every test output carefully, but you want a summary. The prove command from Perl 5 gives you such a summary:

Rakudo is just generally slow, because the focus is on features and correctness first, and speed later.

That said I hope that there will be some improvements before Rakudo Star is released, and if the parrot developers manage to build a good JIT system on top of LLVM until then it might be quite a bit faster.